No required minimum reinforcement in prestressed members: the limiting tensile stress in the concrete σct,p
Eurocode 2 part 1-1: Design of concrete structures 7.3.2 (4)
In prestressed members no minimum reinforcement is required in sections where, under the characteristic combination of loads and the characteristic value of prestress, the concrete is compressed or the absolute value of the tensile stress in the concrete is below σct,p.
The recommended value for the tensile stress in the concrete σct,p is fct,eff which is the mean value of the tensile strength of the concrete effective at the time when the cracks may first be expected to occur:
fct,eff = fctm or lower, (fctm(t)), if cracking is expected earlier than 28 days.